page_title: DNA-encoded chemical library
section_title: DNA-templated synthesis
hierarchical_section_title: DNA-encoded chemical library / Evolution-based technologies / DNA-templated synthesis
caption_attribution_description: English: DNA sequence-programmed chemical reactions
context_page_description: ″DNA-encoded chemical libraries is a technology for the synthesis and screening on unprecedented scale of collections of small molecule compounds. DEL is used in medicinal chemistry to bridge the fields of combinatorial chemistry and molecular biology. The aim of DEL technology is to accelerate the drug discovery process and in particular early phase discovery activities such as target validation and hit identification.
  DEL technology involves the conjugation of chemical compounds or building blocks to short DNA fragments that serve as identification bar codes and in some cases also direct and control the chemical synthesis. The technique enables the mass creation and interrogation of libraries via affinity selection, typically on an immobilized protein target. A homogeneous method for screening DNA-encoded libraries has recently been developed which uses water-in-oil emulsion technology to isolate, count and identify individual ligand-target complexes in a single-tube approach.
context_section_description: In 2001 David Liu and co-workers showed that complementary DNA oligonucleotides can be used to assist certain synthetic reactions, which do not efficiently take place in solution at low concentration. A DNA-heteroduplex was used to accelerate the reaction between chemical moieties displayed at the extremities of the two DNA strands. Furthermore, the "proximity effect", which accelerates bimolecular reaction, was shown to be distance-independent (at least within a distance of 30 nucleotides). In a sequence-programmed fashion oligonucleotides carrying one chemical reactant group were hybridized to complementary oligonucleotide derivatives carrying a different reactive chemical group. The proximity conferred by the DNA hybridization drastically increases the effective molarity of the reaction reagents attached to the oligonucleotides, enabling the desired reaction to occur even in an aqueous environment at concentrations which are several orders of magnitude lower than those needed for the corresponding conventional organic reaction not DNA-templated. Using a DNA-templated set-up and sequence-programmed synthesis Liu and co-workers generated a 64-member compound DNA encoded library of macrocycles.
caption: Fig. 2 DNA-encoded library by ‘DNA-templated synthesis’A library of oligonucleotides (i.e. 64 different oligonucleotides) containing three coding regions was hybridized to a library of reagent compound-oligonucleotide conjugates (i.e. 4 reagent oligonucleotide conjugates), able of pairing with the initial coding domain of the template oligonucleotide. After transferring of the compounds on the corresponding oligonucleotide template, the synthesis cycle was repeated the desired number of times with further sets of carrier compound-oligonucleotide conjugates (i.e. two rounds with four carrier compound-oligonucleotide conjugates per round). Subsequently, functional selection was performed and the sequence of the binding template amplified by PCR. Thus, DNA-sequencing allowed the identification of the binding molecule.
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